Chiral fermions and gauge fixing in five-dimensional theories - art. no. 125014

We study in detail the issue of gauge fixing in theories with one universal extra dimension, i.e. theories where both bosons and fermions display Kalu za-Klein (KK) excitations. The extra dimension is compactified using the st andard orbifold construction for a massless chiral fermion. We carry out th e gauge-fixing procedure at the level of the five-dimensional theory and de termine the tree-level propagators and interaction vertices needed for perf orming perturbative calculations with the effective four-dimensional theory resulting after the compactification. The gauge independence of the tree-l evel S matrix involving massive KK modes is verified using specific example s. In order to obtain massive fermionic zero modes one has to enlarge the t heory by introducing a set of mirror fermions, a construction which is carr ied out in detail. Finally, the gauge independence of the tree-level S matr ix involving the resulting new mass eigenstates is proved by resorting to g eneralized current conservation equations.